Flooded plate heat exchanger

ABSTRACT

The present invention discloses a heat exchanging apparatus including a plate type heat exchanger auxiliary vessel arrangement whereby the auxiliary vessel contains fluid in more than one phase to enable the corresponding plate type heat exchanger to be flooded with heat exchanger fluid in order to fully employ its heat exchange surfaces in the task of exchanging heat.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to improvements in plate type heatexchangers, particularly plate type heat exchangers used as evaporatorsin vapor compression refrigeration, heat pump systems, and dedicatedheat recovery chiller systems.

2. Description of the Related Art

Plate type heat exchangers have been utilized in the past in manyapplications, including vapor compression refrigeration systems.

However, these heat exchangers suffer from a problem, in that whenemployed as an evaporator in a vapor compression refrigeration cycle,they are often just upstream of a compressor. Because liquid platerefrigerant entrained in a gas phase refrigerant flowing from theevaporator into the compressor tends to damage the compressor and alsoreduces its efficiency, fluid emerging from an evaporator is ideallyessentially vapor.

In the past, prior art plate heat exchanger evaporators in theseapplications could not be fully utilized regarding their heat transfercapabilities. Particularly the total available heat exchange surfacearea could not be fully utilized, because a portion of the plate heatexchanger, usually near the top, would be purposely kept essentiallyfree of liquid evaporant, ensuring that eventually any vapor staterefrigerant would exit at the top, adjacent the outlet to the plate typeheat exchanger. In this manner, a portion of the heat transfer area ofthe plates would be used to contain vapor refrigerant just prior toexiting the exchanger, instead being used to evaporate liquidrefrigerant.

The result is that a portion of the plate heat exchanger would beunderutilized for its intended purpose of evaporating liquidrefrigerant.

This situation resulted in plate heat exchangers which were oversizedand meanwhile underutilized for their intended purpose.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed toward providing a plate heatexchanger apparatus which fully utilizes the heat exchanger areas of theplates.

Particularly, the present invention sets out a plate heat exchangerapparatus having an secondary or auxiliary vessel for containing liquid,gas, and/or a liquid-gas mixture.

More particularly, the present invention provides an arrangement foraccommodating fluid exiting a plate heat exchanger which is employed asan evaporator in a vapor compression refrigeration cycle. Thearrangement includes an auxiliary vessel downstream of the evaporatorheat exchanger, upstream of the compressor.

In this manner, the evaporation plate heat exchanger may be filled(flooded) with refrigerant in order to utilize all available plate heatexchange surface area for exchanging heat, while allowing the exitingfluid to travel to the auxiliary vessel, such that substantially onlyvapor exits the auxiliary vessel.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic view of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention sets out a two chamber plate heat exchanger havingan additional chamber for accepting and controlling refrigerant or otherfluid in two thermodynamic phases—gas and liquid. The invention furthersets out a system for utilizing and controlling the fluid in the system.

The inventive two chamber plate heat exchanger may be advantageouslyemployed as an evaporator for refrigerant in a closed-loop vaporcompression refrigerant cycle.

Referring to FIG. 1, a vapor compression refrigeration cycle includingthe present invention is shown.

Refrigerant 11 is condensed to a liquid state 12 in the condenserelement 11 before exposure to the expansion valve 9. The expansion valve9 may be controlled as set out below.

Depending on the position of the expansion valve 9, the thermodynamiccondition of the condensed refrigerant 8 is variously, entirely, inliquid state, or a two-phase liquid vapor state. It is introduced intothe plate heat exchanger 1 which together with the secondary orauxiliary vessel 4 forms the evaporative heat exchanger apparatus of thepresent invention.

The refrigerant in the secondary vessel or auxiliary vessel 4 may be inliquid phase, gas phase, and/or a mixed liquid gas phase.

The secondary vessel 4 may be arranged above or on top of theevaporative plate heat exchanger 1.

Liquid refrigerant 8 is introduced into the evaporative plate heatexchanger 1 at or near a bottom portion of the exchanger 1. Warm fluid 5from the building load 16 which is to be chilled via the phase change ofthe refrigerant in the evaporative plate heat exchanger 1 is introducedinto the exchanger 1. Because the secondary vessel 4 is arranged toaccommodate the gas and non-gas phases of this refrigerant, theevaporative plate heat exchanger 1 can be more effectively utilized toexchange heat from the building load 16 to the refrigerant 8.Specifically, there is no need to allow empty space at the top of theevaporative plate heat exchanger 1 to ensure that no liquid leaves theexchanger en route to the compressor 10 inlet, because the inventiveelement of the secondary vessel 4 is specifically arranged to performthe function of holding and managing the gas and non-gas phaserefrigerant. In this way, the entire surface area of the evaporativeplate heat exchanger 1 can be utilized to exchange heat from thebuilding load 16 to the refrigerant 8.

In another embodiment, the evaporative plate heat exchanger may includea dual refrigerant inlet, to minimize maldistribution of heat and fluidflow in the exchanger.

In one embodiment, a fluid connection is arranged from the bottom of thesecondary vessel 4 to the top of the evaporative plate heat exchanger 1,in order to communicate the refrigerant between the secondary vessel andthe heat exchanger.

The evaporated refrigerant 7 travels through the secondary vessel 4 andexits at the top of the vessel 4. The system is arranged to ensure thatany gas-phase refrigerant 7 exits the secondary vessel 4, while liquidand two-phase fluids remain in the secondary vessel 4, to be deliveredback into the evaporative plate heat exchanger 1 for evaporation, in aclosed-loop manner.

A secondary vessel liquid level sensor 2 monitors the level of liquid inthe secondary vessel 4, and sends a corresponding liquid level signal 3back to the expansion valve controller 18. The liquid level signal 3indicates to the controller 18 whether to variably open or close theexpansion valve 9, in order to supply essentially liquid or gas phaserefrigerant to the evaporative plate heat exchanger 1.

The expansion valve controller 18/expansion valve 9 assembly is arrangedto adjust the thermodynamic characteristics of the refrigerant 12, 8 inorder to supply the secondary valve 4/evaporative plate heat exchanger 1structure with refrigerant 8 in a condition which is determined to berequired for most effective and efficient heat transfer, and energyconsumption in the form of compressor work.

The secondary valve 4/evaporative plate heat exchanger 1 structure maybe utilized in connection with dedicated heat recovery chillers, heatpump systems, and/or conventional chiller refrigeration cycles.

1. An evaporator heat exchanger apparatus comprising: a plate heat exchanger, a secondary vessel disposed at an upper position of said plate heat exchanger, and being in fluid connection therewith, the secondary vessel having at least one fluid inlet and at least one fluid outlet, said secondary vessel containing refrigerant in liquid, gas, and/or a two-phase state, a liquid refrigerant fluid connection connecting the bottom of the secondary vessel and the top of the plate heat exchanger such that substantially all available heat exchanger surface area in said plate heat exchanger is exposed to refrigerant to be evaporated, wherein said secondary vessel contains multi-phase refrigerant, and releases gas phase refrigerant.
 2. An evaporator heat exchanger apparatus according to claim 1, said secondary vessel being contiguous with said plate heat exchanger.
 3. An evaporator heat exchanger apparatus according to claim 1, said secondary vessel being separate from and in fluid connection with said plate heat exchanger.
 4. An evaporator heat exchanger apparatus according to claim 1, said fluid inlet being in fluid connection with said expansion valve, said fluid outlet being in fluid connection with said compressor.
 5. An evaporator heat exchanger apparatus according to claim 1, further comprising an automatically actuated expansion valve, an expansion valve controller, and a secondary vessel fluid level sensor, wherein said expansion valve controller responds to a signal from said secondary vessel fluid level sensor, said expansion valve controller actuating said automatically actuated expansion valve to variously open and close to maintain a liquid refrigerant level at a predetermined level in said secondary vessel.
 6. An evaporator heat exchanger apparatus according to claim 5, wherein refrigerant in said secondary vessel fluid outlet is substantially entirely in gas phase. 